Field of the Invention
The present invention relates to a toner used in an image forming method and a toner jet system for visualizing an electrophotography and an electrostatic image.
Description of the Related Art
As image forming apparatuses such as copying machines and printers have become widespread in recent years, higher image quality is needed, in addition to higher speed and longer life, as a performance feature required for image forming apparatuses.
Reduction in toner particle diameter has been advanced as means for achieving high image quality in the image forming apparatuses. As the particle diameter of the toner becomes smaller, dot reproducibility and fine line reproducibility are improved, but the flowability and charging performance of the toner are likely to be non-uniform.
In particular, when a large number of images of the same pattern are printed, the charging performance and flowability of the toner on the developing sleeve tend to be non-uniform in a printed portion and a non-printed portion. In some cases, where different images are continuously printed while the charging performance and flowability of the toner remain non-uniform, the history of the previous image can be reflected as a difference in a printed image density (hereinafter referred to as “sleeve ghost”).
For example, Japanese Patent Application Publication No. 2016-110095 discloses a technique capable of controlling the toner charging performance and flowability and suppressing a sleeve ghost under a low-temperature and low-humidity environment by adding silica having a number average particle diameter of at least 5 nm and not more than 20 nm and silica having a number average particle diameter of at least 80 nm and not more than 200 nm to a toner.
Yet another problem is that when the charge quantity distribution of the toner on the developing sleeve is broad, in particular when the toner is used over a long period of time under a high-temperature and high-humidity environment, the toner having a low charge quantity is accumulated in the developing device, fine line reproducibility and dot reproducibility are deteriorated, and quality of a fine image may be deteriorated.
Meanwhile, when the particle diameter of the toner becomes small, the toner is unlikely to be scraped by the cleaning blade in the cleaning step, and the toner easily passes through the cleaning blade. In other words, the so-called cleaning defects are likely to occur.
A method of adding strontium titanate to a toner particle has been known as a measure against cleaning defects. For example, Japanese Patent Application Publication No. 2006-195156 discloses a technique for preventing cleaning defects by using a toner including strontium titanate having a number average particle diameter of at least 80 nm and not more than 220 nm and strontium titanate having a number average particle diameter of at least 300 nm and not more than 3000 nm.
Further, Japanese Patent No. 4799567 discloses a technique for preventing cleaning defects by using a toner including composite inorganic fine powder including strontium titanate having a half width of an X-ray diffraction peak at 32.20 deg of 0.20 to 0.30 deg.
Furthermore, Japanese Patent No. 4979517 discloses a technique for improving transferability by using a toner including a composite oxide including strontium titanate having a half width of an X-ray diffraction peak at 32.20 deg of 0.20 to 0.30 deg.